If anyone thinks himself (or herself) to be religious, and yet does not bridle his own tongue but deceives his own heart, this man's religion is worthless.
Worthless means of no use, importance or value. Good for nothing.
James is so straight forward. He tells is like it is. I. need. that.
When a believer does not 'walk the walk' they do NOTHING for God. Sure, I'm still saved if I say unkind things to my friends or the clerk at the store or bank, but I am not helping them. Worthless. When I yell at my kids, worthless. Telling my husband exactly what he did wrong, worthless. Talking about my boss or coworkers behind their backs may not get me in trouble at work, but does it edify? Nope. Worthless.
James goes in to much more detail in Chapter 3. What does he say about my tongue? Well, here is just a snippet.
The tongue is a fire, the very world of iniquity, it cannot be tamed, it is a restless evil and full of deadly poison. Need I go on? Sounds so positive...
So how do I make what I believe NOT worthless? Ephesians 4:29!
Let no unwholesome word proceed from your mouth, but only such a word as is good for edification according to the need at the moment, that it may give grace to those who hear.